Prokaryotes: The big picture



  • ‘Prokaryotes’ are not a monopheyltic group
    • Kingdoms Bacteria & Archaea; each with unique traits
    • most species diverse groups on Earth


  • Diversity of ways of making a living
    • sources of energy to make ATP
    • heterotrophs
    • autotrophs (photosynthesis)


  • Co-evolution with the planet and other organisms
    • oxygen poor to oxygen rich world
    • extremeophiles (temperature, pH, salt,etc.)
    • prokaryotes are most abundant organisms on Earth!

Prokaryotes first to inhabit the Earth


Prokaryotes matter: First fossils




  • First TRACES of living organisms
    • Graphite carbon from Canadian rocks
    • Formed by ‘prokaryotes’
    • ~ 3.9 billion years ago!


  • Cyanobacteria form stromatolites
    • undisputed fossils = 3.5 bya
    • western Australia
    • layers of calcium carbonate precipitated over bacterial colonies

Common ancestor of all species living today: Prokaryote


Prokaryotes are structurally diverse



  • Unicellular (some colonies)


  • Small
    • microscopic to poppy seed


  • Many Shapes
    • spherical, rod, spiral


  • 1/2 are motile (taxis)
    • use flagellum

Prokaryotes do it all! (review Table 27.1)





  • Sources of carbon
    • autotrophs (make themselves)
    • heterotrophs (get from others)


  • Energy for ATP (no mitochondria)
    • sunlight
    • organic molecules
    • inorganic molecules


  • Picture: Bacteria work together
    • photosynthesis and N fixation

Cell surface structures: Gram + & - bacteria


Hospitals: Gram staining as a diagnostic tool



  • 2 main categories of bacterial infections
    • Gram-positive and Gram-negative


  • Gram stain is colored purple
    • If stays purple = Gram-positive
    • If turns pink = Gram-negative


  • Gram+ : MRSA, strep and toxic shock.


  • Gram- : salmonella, pneumonia, UTI’s, and gonorrhea.


Gram - bacteria are more antibiotic resistance


Reproduction in prokaryotes: Binary fision



  • Asexual: daughter cells identical to parent
    • rapid reproduction
    • not sustainable!
    • bad for genetic diversity


  • Mutations are rare but fast reproduction


  • Gene transfer increases diversity:
    • transformation =
    • transduction =

Genetic Recombination: Transformation


Prokaryotes matter: Oxygen Revolution


Prokaryotes matter: Cynaobacteria



  • Cyanobacteria: first evidence ~2.7 bya
    • blue-green algae
    • aquatic and photosynthetic
    • use chlorophyll


  • Photosynthesis evolved independently in distant groups
    • mono, para or polyphyletic?
    • cyanobacteria are a monophyletic group


  • Eukaryotes acquired photosynthesis by engulfing cyanobacteria!

Prokaryotes matter: Great Oxygenation


Prokaryotes matters: Humans

3 domain hypothesis: Linking Prokaryotes and Eukaryotes


2 domain hypothesis: Looking for LUCA